Auxotrophic mutants will be isolated in Candida albicans using a combination of agents which induce mutagenesis and crossing-over. When the technique is perfected, mutants altered in properties likely to be associated with pathogenesis, such as cell-surface molecules, will be isolated and tested for their virulence. Spheroplast fusion as a method of genetic exchange will be tested, as will transformation of Candida albicans auxotrophs with C. albicans DNA cloned in E. coli or Saccharomyces cerevisiae.